Metastasizing ectopic thymoma arising in the right thoracic cavity and mimicking diffuse pleural mesothelioma--an autopsy study of a case with review of literature.

A case of metastasizing ectopic thymoma arising in the right thoracic cavity and infiltrating the right lung and pleura in a fashion reminiscent of diffuse pleural mesothelioma is presented. An involuted, non-neoplastic thymus was demonstrated microscopically in the anterior mediastinum. No case of thymoma showing the combination of ectopic location and biological malignancy has yet been reported in the literature. The pathogenesis of ectopic thymuses and thymomas is discussed from an embryological standpoint. The discrepancy between morphology and biological behaviour of thymomas is also mentioned with a review of the literature.